This invention relates to a film feeding device for use in an endoscope, which can feed a film toward, and wound around, a film takeup shaft of a film cassette provided in the distal end of an endoscope with an equal frame length kept for each film winding operation.
With conventional endoscopes having a photographing optical system and film housed in its distal end, in general, a feeding pulley of a film feeding device in an operation section is rotated through a predetermined rotation angle, causing an operating wire to be wound around the pulley to permit the film to be fed frame by frame.
In one type of known endoscopes in which a film feeding device permits a film to be drawn toward an operation section of an endoscope, a film can be fed at a relatively equal rate.
In another conventional endoscope in which a film cassette having a film takeup shaft is provided in the distal end of the endoscope, a film is wound around the film takeup shaft. Since the diameter of a film roll on the film takeup shaft is gradually increased as the film is wound about the shaft, the frame length of the film is gradually lengthened and, in consequence, the surplus film portions other than the effective image range are gradually increased, requiring a longer film. In this case, such the surplus portion of the film is not effectively used and, further, a bulkier film cassette is required to hold such a larger rolled film and, in consequence, a correspondingly larger distal end is required for the endoscope. Therefore, a difficulty is encountered in inserting such distal end of the endoscope into a required portion of the coelom or body cavity of a human being.